Tubes formed of paper and similar materials conventionally are supported and cut on a cylindrical mandrel which rotates about an axis. At periodic intervals the tube is cut to form a shorter tube or core of selected length which subsequently is removed from the mandrel.
It has been the practice heretofore to cut a tube supported on a mandrel by means of a disc having a cutting edge at its periphery and which is rotatable about its own axis in response to engagement of the cutting edge with the wall of the tube. The cutting disc conventionally is mounted alongside the mandrel for movement substantially radially of the axis of rotation of the mandrel into and out of engagement with the tube. It is necessary that the cutter be moved toward the mandrel a distance sufficient to cut through, or nearly through, the tube wall so as to enable the cut length of tubing to be separated cleanly from the remainder of the tube.
In practice, the cutting edge of the cutter moves into engagement with the mandrel itself, thereby causing dulling of the cutting edge, scoring of the mandrel, or both. These undesirable results are due to a number of factors, among which is the difficulty in stopping movement of the cutter in a direction toward the mandrel in a position in which the cutting edge of the cutter barely engages the mandrel. Such positioning of the cutting edge during a cutting operation is difficult because of problems in defining the precise limit of movement of the cutter toward the mandrel, variations in diameter of the mandrel, and eccentricity of the axis about which the mandrel rotates.
Since the conventional tube cutting mechanisms invariably cause the cutting edges of the cutters to engage the mandrel, and since the force with which the cutting edges engage the mandrel cannot be controlled precisely, dulling of the cutting edges occurs rapidly thereby necessitating frequent renewing of the cutting edges if the severed tubular sections are to conform to predetermined specifications.
An object of the invention is to provide methods and apparatus which overcome or greatly minimize the disadvantages referred to above.